An 18-year-old Aurora man with ties to a foiled attempt last year to bomb a downtown Chicago bar was arrested as he was about to travel to the Middle East to join the al-Qaida terrorist network, federal officials said Saturday.

Abdella Ahmad Tounisi, a U.S. citizen, was held without bail Saturday after being arrested the night before at O'Hare International Airport, where he was about to board an airplane to Istanbul, Turkey, FBI officials said in a press release.

The arrest had nothing to do with the Boston Marathon bombing, officials said.

Tounisi had hoped to eventually join a jihadist militant group operating inside Syria called Jabhat al-Nusrah, according to a federal complaint unsealed Saturday and filed in U.S. District Court. The organization is an alias for al-Qaida in Iraq, the complaint said.

Tounisi allegedly expressed “a willingness to die for the cause” by joining the terrorist group that since November 2011 has claimed nearly 600 terrorist attacks in major city centers in Syria – ranging from more than 40 suicide attacks to small arms and improvised explosive device operations, according to the complaint.

“Concerning my fighting skills, to be honest I do not have any,” Tounisi allegedly wrote to an undercover federal agent who was posing as a recruiter for the terrorist group. “I’m very small (5 feet 6 inches, 120 pounds) physically but I pray to Allah that he makes me successful,” he said, according to the complaint.

He was was charged with attempting to provide material support to a foreign terrorist organization, a felony offense that could bring 15 years in federal prison.

At Tounisi’s home in Aurora, family members declared his innocence, saying that Tounisi was set up by federal agents.

“I know my kid is innocent,” said his father, Ahmad Tounisi. “I know a lot of Muslim kids are getting set up.”

Tounisi said he last saw his son Thursday and he thought he was going to a mosque for three days. He added his son didn't have money to buy an airline ticket to Turkey.

He said FBI agents were in his Aurora home Friday night and took a broken computer, a younger son's Nook and two Xbox systems. Agents also asked to talk to his 13-year-old son but Tounisi denied the request.

Tounisi described his son as a “good boy” who has been studying to become a radiologist at the College of Dupage and who doesn’t like to see others oppressed. Tounisi said his son did talk of going to Syria to fight against injustices to the people, but his father said he would never join a terrorist group.

“I never thought he'd go through with it,” he said, about the plans to go to Syria.

“If I had to tell him anything I would tell him justice is coming,” Tounisi said, adding he believed his son's innocence would be proven.

The complaint links the younger Tounisi with Adel Daoud, who is awaiting trial on federal criminal charges for trying to explode a bomb outside a restaurant bar in Chicago’s Loop.

According to the complaint, Tounisi was a close friend of Daoud, who on Sept. 14, 2012, traveled into Chicago with an undercover agent who brought him to a Jeep that had an inert explosive device in it, officials have said.

Daoud allegedly drove the Jeep to the target — identified by the Tribune as the Cactus Bar & Grill at 404 S. Wells St. — and walked to an alley a block away, where he pulled a triggering device he thought would explode the vehicle, authorities said. The bomb never exploded and Daoud was apprehended and is being held without bail.

“Tounisi and Daoud appeared to share an interest in violent jihad, a topic about which the two exchanged a number of emails, phone calls, and text messages,” according to the complaint filed Saturday.

FBI officials said that in preparation for last year's foiled attack, Tounisi had “recommended certain attack techniques, offered ideas about targeting, and researched those locations online to analyze their feasibility.”

While Daoud allegedly continued his role in the plot, Tounisi backed out in mid-August because he suspected that the person Daoud was working with was an undercover law enforcement officer, according to the complaint. Daoud told the undercover officer that Tounisi wanted to go overseas and join a terrorist group.

According to the complaint, hours after Daoud was arrested, Tounisi was interviewed by FBI agents “and admitted to assisting Daoud in target selection and acknowledged that he had contemplated traveling to Yemen to carry out jihad.”

After Daoud's arrest, Tounisi allegedly continued to research travel to Syria and terrorist organizations. He also applied for and obtained a new passport, officials said.

On March 28, Tounisi made contact with a person he believed to be a recruiter for Jabhat al-Nusrah but who was really an undercover FBI agent, the complaint says. After several emails, Tounisi allegedly wrote that he planned to get to Syria through Turkey.

On April 10, Tounisi purchased an airplane ticket to Istanbul and was given instructions by the undercover agent about how to meet up with “brothers” from Jabhat al-Nusrah who would take Tounisi to a training camp in Syria, officials said.

When Tounisi arrived at O'Hare, he told officials that he was traveling to Turkey to sight-see and that he did not plan to travel to any country but Turkey. He was arrested by FBI officials who had been monitoring his movements.

Tounisi is expected to make an appearance in U.S. District Court on Tuesday.